This invention relates generally to devices for implementing a ground connection between a metallic shield of a cable and a common ground point. More particularly, the present invention relates to clamp devices which mount to fiber optic cables and implement a ground connection via a flexible conductor.
Fiber optic cables are generally buried under ground and typically constructed in a tubular fashion with numerous fiber optic conductors surrounded by a conductive ground shield which is in turn surrounded by a protective jacket of tough flexible plastic or rubber. Many fiber optic cables also include steel cords running the length of the cable, positioned between the conductive shield and the protective jacket, which protect the fragile inner conductors and reinforce the cable. To function properly and safely, cable shields must be grounded at spaced ground points established by regulation and/or operational specifications and practices.
Cable shield ground clamp assemblies are ordinarily positioned within a cabinet, housing or other enclosure to provide a common ground point and shelter for the cables and attached grounding assemblies. Such enclosures are frequently located outdoors and/or underground, where the enclosures and their contents are subjected to intense environmental changes. It is not uncommon for the enclosure to be exposed to moisture in the form of rain, ground water or condensation. Temperature swings from well below freezing to above 100xc2x0 F. are not uncommon.
Establishing reliable electrical connections between the conductive shield of fiber optic cables and a common ground point presents difficulties well known in the art. Conventionally, craft personnel must cut through the protective jacket and expose the metallic shield prior to affixing any clamp or other device for establishing a ground path. Any such cutting or piercing of the protective shield by craft personnel makes the fiber optic conductors and linear strength members susceptible to being damaged, weakened or cut with the potential for delays and costly repairs. Costs are further increased by the specialized training and equipment required to prepare craft personnel to perform the task of cutting the cable shield.
Briefly stated, the invention in a preferred form is a fiber optic shield connector for establishing a reliable ground path from the conductive shield of a fiber optic cable to a common ground point via a flexible conductor. A preferred form of the fiber optic shield connector includes cooperative clamp sections, each composed of electrically conductive, structurally rigid material. Each clamp section includes an open-ended trough defining a longitudinal channel with open, semicircular ends. Linear flanges integrally extend transversely from the trough and contain structures for receiving hardware which joins the two clamp pieces together in a conductive, rigid structure surrounding an open-ended receiving cavity. The structure forming the trough of each clamp section has several threaded openings for receiving grounding screws. Grounding screws threadably engage the threaded openings and penetrate through the clamp material, projecting into the receiving cavity formed by the clamp. Each grounding screw is provided with a sharpened cutting tip surrounding a deep axial recess in the center of the screw.
The clamp is assembled around a fiber optic cable, forming a conductive rigid enclosure with the cable traversing therethrough. The grounding screws are then tightened, penetrating the cable jacket and contacting the conductive shield. The cutting tips penetrate the jacket by cutting a small core of jacket material which is allowed to pass into the deep axial recess of each grounding screw. Several grounding screws are angularly and longitudinally positioned in each clamp section to increase the number and quality of ground contacts with the cable shield. A flexible ground lead is affixed to the clamp and connected to the common ground point.
In another embodiment of the invention, the assembly including the fiber optic cable, shield connector and ground lead is then placed within a molded two piece enclosure. The enclosure includes a box-like tub and mating box-like cover, each surrounding a substantially rectangular interior space with rounded bifurcated notches disposed in the end walls of both the cover and the tub. The notches are aligned so the assembled enclosure has a longitudinal opening which allows the cable to pass through the enclosure. The tub and cover interior spaces may be partially filled with water repellant gel. A durable waterproof enclosure surrounding the ground connection is formed by the mated cover and tub.
An object of the invention is to provide a new and improved connector for establishing and maintaining a high quality ground connection with a fiber optic cable shield.
Another object of the invention is to provide a new and improved fiber optic shield connector which does not require opening of the cable shield prior to installation of the connector.
A further object of the invention is to provide a new and improved fiber optic shield connector that minimizes damage to the fiber optic cable jacket while establishing reliable grounding of the fiber optic cable shield.
A yet further object of the invention is to provide a new and improved fiber optic shield connector which reduces labor costs and craft error.
A yet further object of the invention is to provide a new and improved fiber optic shield connector assembly having improved water, weather and environmental resisting capabilities.
Other objects and advantages of the invention will become apparent from the specification and the drawings.